1. Field of the Invention
The present invention relates to a method for the production of alcohols and, more particularly, to the direct hydration of olefins with water under liquid phase hydration conditions and in the presence of a catalyst to produce said alcohols.
2. Description of the Prior Art
Various direct hydration methods for producing alcohols by hydrating olefins in the presence of an acidic catalyst are well known in the art including vapor phase and liquid phase hydrations under low pressure conditions, or mixed phase and liquid phase hydrations under high pressure conditions, using a fixed bed catalyst, a suspension catalyst, soluble catalyst and the like.
However, in the production of ethanol from ethylene, or isopropanol from propylene, the direct hydration method currently employed on an industrial scale is a low pressure vapor phase method using a fixed bed catalyst of phosphoric acid. This method requires temperatures approaching 300.degree. C. to accelerate the reaction velocity. Moreover, since the reaction is carried out in the vapor phase, it is necessary to maintain a mole ratio of water to the olefin used as starting material at 1 or less and to conduct the hydration reaction under a relatively low pressure, for example, of 40-80 kg/cm.sup.2. As a result, conversion of the olefin is usually only several precent, and cannot be greater than that value due to its chemical equilibrium.
Extensive studies have been conducted on catalystic hydration in a mixed phase or in a liquid phase containing a solid acid such as alumina, silica-alumina, tungsten oxide, molybdenum oxide or chromium oxide, a heteropoly acid containing therein tungsten or molybdenum, an inorganic acid such as phosphoric acid or sulfuric acid, or an organic acid such as sulfonic acid, a carboxylic acid or an acidic ion exchange resin. As typical of such sulfonic acid catalysts, U.S. Pat. No. 3,455,664, for instance, discloses the hydration of water and isopropylene using a catalyst such as sulfonic acid in the liquid phase at a temperature of from 200.degree. to 550.degree. F. under a pressure of from 2,000 to 100,000 p.s.i. U.S. Pat. No. 3,555,080, on the other hand, teaches that sulfonyl-containing fluorocarbon ethers expressed by the formula EQU CF.sub.3 CFHOCF.sub.2 CFXSO.sub.2 M
wherein X is fluorine and M is a hydroxyl group, and derivatives thereof in the sulfonic acid form are useful as an acid catalyst for the acid-catalyzed reaction, but specific and definite examples of such reactions are not illustrated. Further, U.S. Pat. No. 2,830,091 teaches a method wherein an olefin is hydrated in the liquid phase at a temperature of 250.degree.-400.degree. F. and a pressure of 500-3,000 p.s.i. with the aid of a certain fluoridated polycarboxylic acid. However, these known catalysts have disadvantages in one or more of their activity, selectivity, catalytic stability or noncorrosion characteristics and have not yet been put into practical use.